While packet switched services are currently on the rise, transport networks today still rely mainly on circuit switched technology such as SDH (Synchronous Digital Hierarchy), SONET (Synchronous Optical Network), and OTN (Optical Transport Network), where constant rate transport signals transport time-division multiplexed subrate signals. Payload signals are mapped into multiplex units, which in SDH/SONET are termed virtual containers and in OTN are termed ODUk. A multiplex unit represents an end-to-end path through the network and connections in the network are established by configuring the network elements to semi-permanently switch the corresponding multiplex unit, which is present at the same relative position in all consecutive transport frames, along that path.
Network elements are for example add/drop multiplexers and digital crossconnects. Such network elements contain I/O (input/output) ports and a switch matrix interconnecting the I/O ports. The switch function which needs to be performed on the level of multiplex units to establish paths in the network encompasses switching in both, space and time domain, i.e. between different I/O ports and between different timeslot positions. Typically, the transport signals are retimed and aligned at the input port and the switch function is performed on time slots of the aligned signal in synchronism with a common system clock in accordance with a pre-configured interconnection map. Such network elements typically use specialized integrated circuits for I/O and switching functions.
A network node, which makes use of a self-routed cell fabric is known from EP2200200B1. Time-division multiplexed signals are segmented at the input into cells of same length and address information is added to each cell. A first address portion is used in the cell switch for space switching and a second portion is used in on the respective output line card for switching cells belonging to a certain timeslot in the time domain. This mentioned address information is local to the network node, i.e. not visible outside.